Background

Milk thistle has been used medicinally for over 2,000 years, most commonly for the treatment of liver and gallbladder disorders. A flavonoid complex called silymarin can be extracted from the seeds of milk thistle and is believed to be the biologically active component. The terms "milk thistle" and "silymarin" are often used interchangeably.

Milk thistle products are popular in Europe and the United States for various types of liver disease. Although numerous human trials have been published, most studies have not been well designed or reported.

Evidence

DISCLAIMER:
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Chronic hepatitis (liver inflammation):
Several studies of oral milk thistle for hepatitis caused by viruses or alcohol report improvements in liver tests. However, most studies have been small and poorly designed. More research is needed before a strong recommendation can be made.
Grade: B

Cirrhosis:
Multiple studies from Europe suggest benefits of oral milk thistle for cirrhosis. In experiments up to five years long, milk thistle has improved liver function and decreased the number of deaths that occur in cirrhotic patients. Although these results are promising, most studies have been poorly designed. Better research is necessary before a strong recommendation can be made.
Grade: B

Acute viral hepatitis:
Research on milk thistle for acute viral hepatitis has not provided clear results, and milk thistle cannot be recommended for this potentially life-threatening condition.
Grade: C

Amanita phalloides mushroom poisoning:
Milk thistle has been used traditionally to treatAmanita phalloidesmushroom poisoning. However, there are not enough reliable studies in humans to support this use of milk thistle.
Grade: C

Cancer:
There are early reports from laboratory experiments that the chemicals silymarin and silibinin in milk thistle reduce the growth of human breast, cervical, and prostate cancer cells. There is also one report of a patient with liver cancer who improved following treatment with milk thistle. However, this research is too early to draw a firm conclusion, and effects have not been shown in high-quality human trials.
Grade: C

Diabetes (in patients with cirrhosis):
A small number of studies suggest possible improvements of blood sugar control in cirrhotic patients with diabetes. However, there is not enough scientific evidence to recommend milk thistle for this use.
Grade: C

High cholesterol:
Although animal and laboratory research suggests cholesterol-lowering effects of milk thistle, human studies have provided unclear results. Further studies are necessary before a firm recommendation can be made.
Grade: C

Liver damage from drugs or toxins:
Several studies suggest possible benefits of milk thistle to treat or prevent liver damage caused by drugs or toxic chemicals. Results of this research are not clear, and most studies have been poorly designed. Therefore, there is not enough scientific evidence to recommend milk thistle for this use.
Grade: C